A rolling bearing forming a wheel and hub assembly provides an inner ring, which rotates in use, having a flange to support a vehicle wheel, and an outer ring, which is stationary in use; a radial annular space between the inner and the outer ring houses the rolling bodies designed to make the inner and outer ring freely rotatable relative to one another about a common axis of symmetry. To protect the rolling bodies, a sealing device is arranged between the inner and the outer ring on the side of the wheel flange. A suitable sealing device is known from US2013/0127119A1, and provides a first annular shield fixed to the rotating ring and a second annular shield fixed to the stationary ring. The second shield is integrally equipped with an annular elastomeric sealing element designed to exert a static sealing action on the stationary ring and a sliding, or “dynamic”, sealing action on the first shield by means of one or more elastic sealing lips projecting from the second shield towards the first shield.
In order to reduce the friction of the seal, provision is typically made to reduce the contact force with the sealing lips, or to reduce the number of sealing lips in contact with the sealing device, but this has a negative effect on the sealing capacity of the device. To reduce or eliminate this problem, a pre-sealing operation is performed in the device to prevent water or mud from reaching the contact sealing lips of the device which provide a sliding seal. However, the implementation of this function requires sufficient space to develop adequate labyrinth seals, resulting in sealing devices such as that of US2013/0127119A1, with rather large overall dimensions.
Moreover, the axial positioning of the sealing lips in contact is frequently affected by the elastic reaction of the elastomer provided in the sealing device to apply the static sealing action, resulting in a contact force of the sealing lips which may be too low or too high, thus rendering the sliding sealing action unreliable.
Finally, the known sealing devices may frequently have a limited static sealing action, particularly in the axial direction; however, the provision of more space causes the rings of the bearing to become larger and heavier.